1. Field of the Invention
The present invention relates to breathing circuits and more specifically to medical applications of low pressure oxygen breathing circuits.
2. Description of the Related Art
An increasing number of surgical procedures are being performed in doctor's offices. This in turn creates many challenges that have to be faced every day in the field of anesthesia. Anesthesia machines are one major type of anesthesia care and include assisted and/or artificial ventilation systems that provide an artificial atmosphere to a patient. These machines supply patients with fresh gases for breathing and remove expiratory waste gases. Fresh gases include inhalation anesthesia agents in combination with other gases, such as oxygen. Anesthesia is typically supplied continuously at flow rates between four and eight liters per minute.
The conduits that supply and remove the artificial atmosphere are commonly referred to as breathing circuits and have a variety of well known configurations such as, for example, those of the Mapleson and Bain breathing circuits. Anesthesia machines employ specialized anesthesia breathing circuits to deliver the fresh gases at high pressures. These breathing circuits have evolved into breathing circuit systems that use many conventional and standardized devices. Conventional devices as defined herein are devices approved for use in medical applications. Standard or standardized devices are those devices that have specific mechanical properties that have become widely used in the industry. For example, standard sized diameters tubes for breathing circuits and standard interfaces for connectors.
Anesthetizations are inherently complex procedures that are vulnerable to a wide range of problems. For example, medical staffs cannot wholly trust that patients have complied with their pre-anesthesia instructions and have arrived for their surgical procedure in a proper condition. During the surgical procedure, a slight movement of the patient's body can create a major disaster and result in permanent damage to the patient's body. Concerns such as these drive a strong preference by surgeons for well controlled patients in deep sedation.
Deep sedation, however, poses a number of risks including an increased likelihood that the patient's breathing will be interrupted. For example, deep sedation causes the patient's muscles to relax, including those surrounding the patient's airway and these muscles can restrict the airway. Thus, a patient's airways have to be constantly monitored for carbon dioxide build-up and/or maintained in the open position in order to prevent any breathing interruption. When the airway closes, the flow of fresh gases is interrupted, the patient can quickly reach a state of hypoxia and permanent damage to the patient.
Traditionally, most anesthesiologists are hesitant to implement the technique of providing a patent airway maintaining device to patients where deep sedation is required in an office procedure. In contrast, for the safety of the patients' airway, the Anesthesia Patent Safety Foundation requires that if a patient is under deep sedation, the airway must be made secure and an exhale carbon dioxide monitor as well as an oxygen saturation monitor must also be used. These measures are only possible when the patient's airway is secured by a patent airway maintaining device. The reality is, however, due to the lack of funding and poor planning, many doctors' offices are not always in full compliance with the requirements of the Anesthesia Patent Safety Foundation.
In many situations, however, anesthesia machines are not available for deep sedation due to their size, expense, particular concerns about the patient, cost or time constraints and a patient's airway is at risk. In these situations, intravenous narcotics and sedatives can be used to achieve deep sedation. While deep sedation using anesthesia machines typically requires the use of a patent airway device, intravenous deep sedation does not always use a patent airway device and as a result can have amplified risks. Deep sedative drugs depress the breathing center in the brain, which depresses respiration and suppresses swallowing reflexes. A further reduction in the patient's already shallow breathing can easily occur and is not necessarily readily detectable. This can lead to a carbon dioxide build up in the patient's body and patient may develop acidosis.
Deep sedation is also commonly used in conjunction with diagnostic equipment such as MRIs and radiographic machines. Diagnostic procedures using these machines require a completely relaxed and cooperative patient. This is not possible without the help of sedative drugs. Thus, usually non-MRI or other radiographic procedures require patients to be intubated or placed on a ventilator with intravenous sedative agents. The inability of the MRI procedure to accommodate metals, limits the ability of ventilators to be employed with patients. This creates a serious risk, since a deep sedative drug depresses respiration and swallowing reflexes. If the airway is not maintained, the patient can become hypoxic or aspirate in this situation as well.
In contrast to anesthesia breathing circuits, oxygen breathing circuits solely supply oxygen to patients and can be as simple as a source of oxygen connected to a face mask. Within this broad range of anesthesia and oxygen devices, however, there is a gap in which patients are at risk: there is a need for a breathing circuit that can intubate and supply low pressure oxygen to patients where there is an inherent risk of hypoxia with or without anesthesia. This at risk area of patients includes patients that are anesthetized without an anesthesia machine that are breathing normally. Another area of risk is those patients that are responsive, but not breathing normally. Still another area of risk is patients that are not anesthetized that are unresponsive and/or breathing abnormally due to trauma, for example.
An oxygen breathing circuit is needed that supplies low flow rates of oxygen directly into an airway maintaining device of a patient that has a low flow resistance, reduces dead space, does not interfere with diagnostic machines and can selectively provide assisted ventilation.